Error : Index was outside the bounds of the array. [duplicate]

I'm aware of what the issue is stating but I am confused to how my program is outputting a value that's outside of the array..

I have an array of ints which is 0 - 8 which means it can hold 9 ints, correct? I have an int which is checked to make sure the users input value is 1-9. I remove one from the integer (like so)

if (posStatus[intUsersInput-1] == 0) //if pos is empty { posStatus[intUsersInput-1] += 1; }//set it to 1 

then I input 9 myself and I get the error. It should access the last int in the array, so I don't see why I'm getting an error. Relevant code:

public int[] posStatus; public UsersInput() { this.posStatus = new int[8]; } int intUsersInput = 0; //this gets try parsed + validated that it's 1-9 if (posStatus[intUsersInput-1] == 0) //if i input 9 it should go to 8? { posStatus[intUsersInput-1] += 1; //set it to 1 } 

Error:

"Index was outside the bounds of the array." "Index was outside the bounds of the array." 

3 Answers

You have declared an array that can store 8 elements not 9.

this.posStatus = new int[8]; 

It means postStatus will contain 8 elements from index 0 to 7.

public int[] posStatus; public UsersInput() { //It means postStatus will contain 9 elements from index 0 to 8. this.posStatus = new int[9]; } int intUsersInput = 0; if (posStatus[intUsersInput-1] == 0) //if i input 9, it should go to 8? { posStatus[intUsersInput-1] += 1; //set it to 1 } 

//if i input 9 it should go to 8?

You still have to work with the elements of the array. You will count 8 elements when looping through the array, but they are still going to be array(0) - array(7).